1. Model of relationship between ventilation and perfusion.
Model of relationship between ventilation and perfusion. Even when the gases at the blood-gas barrier are in complete equilibrium, the composition of effluent (expiratory) gas differs from that of alveolar gas because effluent gas also contains gas from the alveolar dead space (whose composition is that of the inspired gas). Similarly, the composition of arterial blood differs from that of capillary blood to the extent that it is mixed with shunt blood (whose composition is that of mixed venous blood). This concept (the calculation of the difference between expected composition and actual composition of the effluent media) is the basis for calculating both alveolar dead space and shunt.
Gaston Murias et al. Respir Care 2014;59:
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